When to Perform Urine Albumin-to-Creatinine Ratio Testing
Screen all adults with diabetes, hypertension, cardiovascular disease, chronic kidney disease, or a family history of kidney disease annually using a spot urine albumin-to-creatinine ratio, starting at diagnosis for type 2 diabetes and 5 years after diagnosis for type 1 diabetes. 1, 2
Initial Screening by Population
Diabetes Mellitus
- Type 1 diabetes: Begin ACR screening 5 years after diagnosis 3, 2
- Type 2 diabetes: Begin ACR screening immediately at diagnosis due to uncertain disease onset 3, 2
- Screen annually thereafter using first morning void urine samples 3, 2
Hypertension
- Screen annually, as over 20% of hypertensive patients have undiagnosed albuminuria (ACR ≥30 mg/g), yet only 7% are currently tested 2
Cardiovascular Disease
- Screen annually, as CKD prevalence exceeds 40% in this population 2
Chronic Kidney Disease
- Test all people at risk for CKD using both urine albumin measurement and eGFR assessment 1
- Adults with one or more CKD risk factors should be assessed every 1-2 years depending on risk-factor profile 4
Family History
- Annual screening for individuals with a family history of CKD or end-stage renal disease 2
Confirmation of Abnormal Results
Any ACR >30 mg/g requires confirmation with 2 out of 3 positive tests collected over 3-6 months before diagnosing persistent albuminuria. 3, 2, 5
Exclude Transient Causes Before Confirming
- Active urinary tract infection or fever 3
- Congestive heart failure exacerbation 3
- Marked hyperglycemia 3
- Menstruation 3
- Uncontrolled hypertension 3
- Exercise within 24 hours 3
Monitoring Frequency After Initial Diagnosis
Based on ACR and eGFR Categories
| ACR Category | eGFR (mL/min/1.73 m²) | Monitoring Frequency |
|---|---|---|
| <30 mg/g (normal) | Any | Annually [3,2] |
| 30-299 mg/g | ≥60 | Annually [3,2] |
| 30-299 mg/g | 45-59 | Every 6 months [3,2] |
| 30-299 mg/g | 30-44 | Every 3-4 months [3,2] |
| ≥300 mg/g | >60 | Every 6 months [3] |
| ≥300 mg/g | 30-60 | Every 3 months [3] |
| Any ACR | <30 | Immediate nephrology referral [3] |
After Treatment Initiation
- Retest within 6 months after initiating antihypertensive therapy or lipid-lowering treatment to assess response 2
- If treatment achieves significant reduction in albuminuria, return to annual monitoring 2
Optimal Collection Method
Use first morning void specimen for all patients to minimize variability and avoid orthostatic proteinuria. 3, 2, 5
- If first morning void is not possible, a random spot urine sample is acceptable 3, 4
- Spot untimed urine samples are preferred over 24-hour collections, which are burdensome and add little accuracy 2, 5
- Collections should be at the same time of day when possible 3
- Patient should not have ingested food for at least 2 hours prior to collection 3
Special Considerations
Pregnancy
- Following incidental detection of elevated ACR, repeat tests to confirm presence of CKD 1
Unexplained Renal Signs
- Do not assume chronicity based on a single abnormal eGFR or ACR, as this could represent acute kidney injury or acute kidney disease 1
- Proof of chronicity requires duration of minimum 3 months, established by repeat measurements or review of past measurements 1
Heart Failure
- Screen for albuminuria, as it is associated with cardiovascular mortality and may reflect widespread endothelial dysfunction 6
Clinical Pitfalls to Avoid
- Do not rely on a single elevated ACR value for diagnosis—high day-to-day variability necessitates confirmation 3, 5
- Do not use 24-hour urine collections routinely—spot ACR is more convenient and equally accurate 2, 5, 7
- Do not ignore values in the "high normal" range (>10 mg/g)—even ACR values below 30 mg/g carry prognostic significance for CKD progression in diabetes 8
- Do not delay treatment initiation while waiting for chronicity confirmation if CKD is deemed likely due to other clinical indicators 1